Production of water gas



Nov. 3, 1953 F. T. BARR ET A1.

PRODUCTION oF WATER GAS Filed Aug. 15, 194e Nm O mmJOOo o m o Frank 7'.Barr Karl J. Nelson Inventors Attorney 3 and without troubles arisenfrom ash fusion or softening.

These difficulties are particularly pronounced when the gasificationreaction is to be carried out under elevated pressure above say 20 lbs.per sq. in. gauge because the rate of steam conversion drops rapidlywhen the pressure is increased and this drop in rate of conversion mustbe compensated for by a corresponding increase in ternperature orincrease in contact time.

The present invention overcomes the aforementioned dimculties andaffords various additional advantages. These advantages, the nature ofthe invention and the manner in which it is carried out, will be fullyunderstood from the following description thereof read with reference tothe accompanying drawing.

1t is, therefore, the principal object of our invention to provide animproved process for the production of gas mixtures containing carbonmonoxide and hydrogen.

Another object of our invention is to provide a process for theproduction of Water gas from carbonaceous materials and steam involvingan increased conversion of steam by more economical means.

A more specic object of our invention is to provide an improved processemploying the fluid solids technique for the production of Water gas byreacting solid carbonaceous materials with steam and supplying heat ofreaction by the combustion of carbonaceous materials.

Other objects and advantages of our invention will appear hereinafter.

We have found that these objects may be accomplished quite generally byemploying in a fluid gas generator solid carbonaceous charging materialof relatively high chemical reactivity. In this manner, the steamconversion at a given temperature and under otherwise equal conditionsmay be considerably increased and the gas generator may be operated attemperatures considerably below the gas generation temperatures requiredfor other feed material under similar conditions of pressure, steamconcentration, contact time, carbon concentration, etc. withoutdetrimentally affecting the steam conversion.

In general, carbonaceous solids which have an oxidation reactivity ofT15 of 200-250 C. and of T75 of 250-300 C. are suitable for ourprocess.1 Our preferred highly reactive carbonaceous starting materialis low temperature coke obtained by carbonizing coal at temperatures notsubstantially higher than 1000 F., and preferably within the range of600 to 950 F., to an oxidation reactivity of about T15=200210 C. andT75: 250-260 C. When low temperature coke of this type is charged to afiuid gas generator the gasiflcation temperature may be lowered as muchas about 100200 F. beneath the level'required for conventional chargingmaterials such as coal or high temperature coke, without affecting steamconversion under otherwise equal conditions. Substantially completesteam conversion of 98 to 99% may be achieved at temperatures in theneighborhood of about 1900" F., While at 1700 F. the steam conversionstill amounts to about 80% Gas generator plugging which may be adangerin fixed bed operation as a result of the use of a charge of lowmechanical strength is avoided when the fluid soli-ds technique isapplied. Thus,

per minute and 75 C. per minute respectively` '4 the gas generationreaction may be efticiently conducted below the upper temperature limitsdrawn by the heat resistance of economic construction materials and theash fusion or softening point.

Other suitable highly reactive charging materials include certainbituminous or sub-bituminous coal, lignites, brown coals, etc. uncokedor coked, at temperatures not substantially above 1000 F. preferablybetween about 600 and 1000 F., whose oxidation reactivity falls withinthe limits indicated above. Whenever a preparation such ascarbonization, drying, oxidation, etc. of the charging material isrequired or advisable in order to attain the desired high degree ofreactivity, we prefer to employ the fluid solids technique for thepurpose because this technique affords the greatest advantages withrespect to temperature control and constancy as well as uniformity andconstancy of product composition and reactivity.

The heat required for the gasification reaction and charge preparationis preferably generated by combustion in a separate heater andcirculation of highly heated solid combustion residue to the zones ofheat consumption, although combustion within the latter zones by meansof air and/or oxygen may be applied instead or in addition to a separateheater, if desired. Thus, when employing the fluid solids technique, weprefer to use a system similar to that described in the copending F. T.Barr application, Serial Number 619,874 led October 2, 1945, whereincarbonaceous residue from a fluidized gas generator bed is subjected inthe form of a fiuidized bed to combustion in a separate heater and thesensible heat of hot combustion residue is used to supply the heatrequired in the gas generator. No matter, however, which method of heatsupply is chosen the advantage of increased steam conversion or reducedgasification temperature will be fully realized when using our highlyreactive gasification charge outlined above.

In application Serial No. 702,992, filed in the name of Frank T. Barr onOctober 12, 1946, there is set forth the concept that in the lowtemperature carbonization of carbonizable solids undesired tar fractionsare recycled to the carbonization zone to be converted into gas, lightoils and coke whereby the yields of desirable products and thereactivity of the coke in the Water gas reaction are increased.

Having set forth its general nature and objects, our invention will bebest understood from the subsequent more detailed description in whichreference will be made to the accompanying drawing which illustrates asystem suitable for carrying out the preferred embodiment of theinvention.

Referring now in detail to the drawing, a solid carbonizable fuel iscrushed or pulverized in crusher I to a finely divided form, forexample, of the order of 50% having a size of less than mesh, thoughsmall lumps of up to 1/4 or 1k inch size may be used. For the purposesof the following description, the carbonaceous material will be referredto as a bituminous carbonization coal containing 30-35% volatile matter,but other materials can be used.

The properly sized carbonization coal is hoisted or conveyed inanymanner known per se through line 3 to feed hopper 5. From here it isfed through line Inprovided with screw feeder I4 into pipe I8 providedwith control valve I9 and then into a dispersing chamber 20. Thevnnely4.attacca divided coal is dispersed in dispersingl chamber in a streamof fluidizing gas, such as superheated steam, nitrogemilue gases,Acarbcnization gases or vapors, or the like, 'supplied through line 22by compressor 24. `The solids in thedispersion are now in the so-callediluidized state` in which they are capable of flowing through pipes,vvalves, etc. similar to a liquid and exhibiting staticand dynamic heads.

The 'iluidized coal enters rthefconical lower portion` of the enlargedcylindrical carbonization chamber 26 and passes through a distributinggrid 21 into the carbonization zone 28 wherethe carbonizaticn coal issubjectedrin the'form of ,-a dense ebullient uidized mass'forming awellnelined upper level 29 to coking temperatures of ybetween about 600and 950 F.,Ipreferably. around 900 F. The heat required for thecarbonization reaction is preferably supplied by highlyheated solidsrecirculated from combustion chamber v60 through line 65 as will appearmore clearly hereinafter. Volatile carbonizaticn products containingsmall amounts of solids .nes,are-passed through a gassolids separator`39 :which maybe a centrifugal or electric typeprecipitator, and throughline 32 to any conventional system 34for the recovery of such volatileVcarbonization products as coal gas, oil, tar, chemicals, etc. Undesiredtar fractions may be returned through l'line 35 to chamber 26 to beconverted` into` gas in the course of the carbonization treatment.Solids separated in 30 are recycled through pipe 3l to the dense phasein 28.

Fluidized low temperature carbonization coke is withdrawn fromcarbonization chamber 26 ata Y.

point above grid 21 through pipe-36, and passed through control valve 31todispersingconduit 38 where it is taken up by highly heated steamsupplied from steam preheater v through line 40. From dispersing conduit38 the liluidized coke is passed through line 39 into the lowerv conicalportion of the cylindrical gas generator 42 provided with distributinggrid 43 in an arrangement similar to that of carbonization chamber 26.

The gas generator is maintained ata temperature of between about 1600and 1900 preferably about 17001800 F. and a pressure ,of about 40-60lbs. perV sq. in. gauge to permit the Water gas reaction to take placebetween the steam and the coke maintained-in a dense, ebullient mass 44forming a level 45 in generator42. The heat required for the AWater gasreaction'is supplied by highly heated solid lresidues recirculated fromcombustionzone .60 through line 69 at the desired temperature, as willappear more clearly hereinafter. At these conditions, the conversion ofsteam to carbon monoxide and hydrogen amounts to about 80 to 90% of thetheoretical as compared with about `30 to 60% when a conventionalgasication charge such as high temperature coke is used. LThe relativeamounts and the contact time of coke-and steam vsupplied to generator 42are so controlled that about 80 to 90% of the steam is converted' to andCO and about 80 to 98% of the coke iserficiently utilized in thecombined heat and water gas generation.

A gas consisting mainly of carbon monoxide and hydrogen is takenoverhead from generator 42 and freed in gas-solids separator 46 fromentrained lines which may be returned through pipe 48 to the dense phase44. The gas leaves separator 46 through line 49 and passes throughadmitted through linei, toa cooling systemi? `from which 'it -may bewithdrawnfor any desired useas afuelgas, )for hydrocarbon synthesis, andothers. ,Tower 52 may. also be ascrubberior removal of any traces ofsuspended solidsnot separated rin 46. The st'eampreheated vin 350'passes' through line 40 to dispersng conduit'SB, as, outlined above.

@Solid carbonaceous gasification residue is with.` 'drawn throughvertical pipe .53 from `a point above grid 43 and passed through controlvalve 55 to ;dispersing conduit 56 Where it is taken up 'byshot air,oxygen, or other oxidizing gas supplied through line51, as will appearmore clearly below. f The mixture of solid gasification residue andoxidizing gas passes 'at about the temperatureof `tl'iegasiiication zonethrough line 59 to the conical lower portion of the cylindrical com-:bustion chamber -60 lwhich has a construction similar tothat ofchambers 26 and 42j and serves as a heater for zones' 26 andl42.",I'hesolids-gas mixture enters the cylindrical portion of heater -60through a distributing grid 6l `and Vforms thereabove a liluidized denseebullient phasej'62 having a weil dened upper`A level 63, YThetemperatureof zone 62v is maintained, between l700 and 2000 F.preferably at about'1800" to 1900 F. Solid combustionresidue consistingessentially of coal ash is returned from `a pointabove grid 6i at .aboutthe temperature of` the combustion zone B2' through-vertical .pipe B5provided ,with control valve 61 to the lower ,portion of carbonizationchamber 26in amounts suflieient to supply theheat required forcarbonization. This amount may vary .betweenabout and "200% by weight ofthe solids charged through Yline 20, depending on the temperature.difference between combustion zone 62 and carbonization Azone 28, goodresults being, in general'obtained zat a solid recycle ratio of.about-100% to 150%. Axfluidizing gas may be supplied by compressor.424; through lineBB tu facilitate Vthe transport of the solidthroughline 65. Y VAnother considerably larger amount of solid combustionresidue is withdrawn from above grid lil through vertical pipev69providedwith control vvalve 1| to .be returned through line39 to. gasgenerator 42 to supply the heat required in gast- '.cation zone 44. Inaccordance with the considerably higher temperature ,and thev normallylarger dimensions of gasgenerator42, the amount vof solids recycled to42 visa `high'multiple of that recycled to carbonizationrchamberZB and.may *vary between the approximate limits of 30 tos-30,0 times thecarbon content of the solids charged through line 36 or may be about20to 100 times the amounts of vrsolidsreturnedA through line 65.

Flue 4gases are withdrawn overhead `from heater 50 throughgas-solidsseparator 12 where they are freed from solid-fines.l The lines .may bereturned through vertical; pipe "13 to Y the dense phase 62 Aorwithdrawn from the system. `Hot lluegassubstantially free of 'A'solidsis passed through -iine 15 to-air preheater 'i6 where it; pre- -heatsthey air` supplied by compressor 'le through "line 1-9. "Thepreheatedair passes through line 51 into dispersing eenduitf 56as-shown above.Flue gas, if desired after further dust removal in 80, may then beapplied to any desired use, such as the operation of a ilue gas turbine82, for heat recovery, or discarded.

The supercial gas velocity in reactors 25, 42, and 60 are those commonlyused for the fluidization of dense beds of solids of the particle sizesteam preheater 50 in heat exchange with steam 75 indicated and mayrange from about 0.3 to 10 ft,

per second, preferably between about0.5 to 3 ft. per second. Thepressure of the system may be .essentially atmospheric but is preferablykept within the approximate limits of 40 to 200 lbs. per sq. in. gaugeto save compression on the gas manufactured. Higher pressures may beused as feasibility and economy of contruction techniques allow,particularly if water gas of high B. t. u. value is desired. Ourinvention is particularly well adapted to high pressure operation sincehigh steam conversion can be obtained at reasonable temperature even atthe highest pressures desirable for gasication.

Means may be provided to withdraw ash from suitable points of the systemin any manner known per se, for instance from pipes 65 and/or 69 inorder to avoid a build up of ash in the system. If desired, an oxidizinggas such as air and/or oxygen may be supplied to chambers 26 .and/or 42to generate heat by combustion therein, in order to supplement orreplace the heat :supplied from heater 66. Other modifications of ourinvention will appear to those skilled in the Aart.

Our invention will be further illustrated by the following specificexample.

Example The superiority of the process of the invention over thegasification of a conventional gasification charge is illustrated by thedata given below which summarize the essential conditions of water gasmanufacture in a system of the type specifically described above andillustrated in the drawing, using conventional gasification feed on theone hand and gasification feed of the invention on the other hand.

Raw Coal inspection:

Ash, percent 8.0 Volatile matter, percent 37. Fixed carbon, percent 54.5 t. u 13, 71o Fusion temperature. F 2,150

Conventional Present Gas- Gasication ifieation Feed Feed CarbonizationTemperature, F 1,700 900 Coke Reactivity:

T, 415 205 T75, 495 25o Gasication Temperature, 1,800 1, 800 GasicationPressure, p. s. i. g. 45 45 Fluid Bed Height, Ft 32 32 Fluid BedDensity, Lbs/O. F 20 Inlet Steam Velocity, FtJSec 0. 5 0. 5 CarbonConcentration, Wt. Per nt of Solids 20 2f) Steam Conversion, Wt. Percent50 90 The above data demonstate that steam conversion may be almostdoubled when operating in accordance with the present invention underotherwise equal conditions.

While the foregoing description and exemplary operations have served toillustrate specific applications and results of our invention, othermodifications obvious to those skilled in the art are within the scopeof our invention. Only such limitations should be imposed on ourinvention as are indicated in the appended claims.

We claimt 1-. The process of producing gas mixtures con'- taining carbonmonoxide and hydrogen from solid carbonaceous materials and steam whichcomprises contacting steam in a gasification zone at gasificationtemperatures with a dense ebullient mass of finely divided carbonaceoussolids fluidized by an upwardly fiowing gas to resemble a boiling liquidhaving a well defined upper level. said carbonaceou's solids being lowtemperature carbonization coke formed by coking carbonaceous material ina coking zone at temperatures within the range of from about 600-900 F.to produce a coke having an oxidation reactivity of about T15=200210 C.and T75=250260 C. to produce carbon monoxide and hydrogen when treatedwith steam at gasification temperatures, withdrawing coke from saidcoking zone and passing it directly to said gasification zone, with`drawing solid carbonaceous gasification residue from said gasificationzone and passing it to a combustion zone, subjecting said solidcarbonaceous gasification residue to combustion with an oxidizing gas insaid combustion zone to generate heat and supplying heat of combustionto said gasification zone as sensible heat of finely divided combustionresidue returned to said mass by withdrawing hot carbonaceous solidsfrom said combustion zone and passing them with said carbonaceous solidswithdrawn from said coking zone to said gasification zone.

2. The process of claim 1 in which said gasification is carried out at apressure above 40 lbs. per sq. in. gauge.

3. The process of claim l wherein the solids in said separate combustionzone are maintained in the form of a dense ebullient mass of finelydivided solids fluidized by an upwardly flowing gas to resemble aboiling liquid having a well dened upper level.

FRANK T. BARR. KARL J. NELSON.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,776,876 Winkler Sept. 30, 1930 1,857,799 Winkler May 10,1932 2,187,872 Winkler et al. Jan. '23, 1940 2,436,938 Scharmann et al.Mar. 2, 1948 2,482,187 Johnson Sept. 20, 1949 2,579,398 Roetheli 1 Dec.18, 1951 FOREIGN PATENTS Number Country Date 310,686 Great Britain May2, 1929 OTHER REFERENCES Morgan: A Textbook of American Gas Practice,vol. I, pp. 874-875.

Lowry: Chemistry of Coal Utilization, vol. I, 1945, pp. 774, 775, 897,900.

Wilson et al.: Coal, Coke and Coal Chemicals, Chemical EngineeringSeries (1950). pages 4 18 and 419.

1. THE PROCESS OF PRODUCING GAS MIXTURES CONTAINING CARBON MONOXIDE ANDHYDROGEN FROM SOLID CARBONACEOUS MATERIALS AND STEAM WHICH COMPRISESCONTACTING STEAM IN A GASIFICATION ZONE AT GASIFICATION TEMPERATURESWITH A DENSE EBULLIENT MASS OF FINELY DIVIDED CARBONACEOUS SOLIDSFLUIDIZED BY AN UPWARDLY FLOWING GAS TO RESEMBLE A BOILING LIQUID HAVINGA WELL DEFINED UPPER LEVEL, SAID CARBONACEOUS SOLIDS BEING LOWTEMPERATURE CARBONIZATION COKE FORMED BY COKING CARBONACEOUS MATERIAL INA COKING ZONE AT TEMPERATURE WITHIN THE RANGE OF FROM ABUT 600*-900* F.TO PRODUCE A COKE HAVING AN OXIDATION REACTIVITY OF ABOTU T15=200*-210*C. AND T75=250* C. TO PRODUCE CARBON MONOXIDE AND HYDROGEN WHEN TREATEDWITH STEAM AT GASIFICATION TEMPERATURES, WITHDRAWING COKE FROM SAIDCOKING ZONE AND PASSING IT DIRECTLY TO SAID GASIFICATION ZONE,WITHDRAWING SOLID CARBONACEOUS GASIFICATION RESIDUE FROM SAIDGASIFICATION ZONE AND PASSING IT TO A COMBUSTION ZONE, SUBJECTING SAIDSOLID CARBONACEOUS GASIFICATION RESIDUE TO COMBUSTION WITH